A conventional lat pulldown fitness device comprises supports, a bar, a cable, a plurality of pulleys, a plurality of bumper plates, and a seat. The pulleys are disposed on the supports. The cable straddles the pulleys and has two ends connected to the bumper plates and the bar, respectively. A user applies a force stronger than the weight of bumper plates to pull the bar downward repeatedly in order to exercise muscles. To adjust the applied force required for pulling the bar downward in order to exercise muscles, the user adjusts the pins of bumper plates in the lat pulldown fitness device in order to choose the weight required for a desirable strength level.
During a workout, the user has to stop exercising muscles for a while in order to remove the pins by hand and adjust a load weight. Furthermore, it is possible that the user inserting the pins in place stays so close to the bumper plates that the user might get hurt whenever a bystander pulls the bar inadvertently. Moreover, the conventional lat pulldown fitness device uses one bumper plate as a weight adjusting unit which has its limits on strength adjustment and selection. The commonest scenario of difficulty in strength adjustment and selection is that: the user is dissatisfied with the preceding weight chosen for the intended strength level but is exhausted when exercising muscles with the present weight chosen for the intended strength level, and in consequence the user fails to comply with the workout plan and meet the workout need.
Furthermore, in the absence of a fitness coach, the user is likely to exert forces so improperly that the bumper plates collide with each other or fall, thereby generating noise—terrifying neighbor users and damaging fitness equipment. In the absence of a fitness coach, the user is also likely to have his or her arms and shoulders injured while his or her hands are gripping the bar, because the total weight of the bumper plates outweighs the force generated from the user's hands, and thus the bumper plates fall to strain the user's arms and shoulders.